- Enantioselective Synthesis of Cyclohexenol Derivatives from ?-Aryl-Substituted Enals via an Organocatalyzed Three-Component Reaction
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A three-component reaction between ?-aryl-substituted α,β-unsaturated aldehydes and nitroalkenes was realized by using cinchona alkaloid-derived (thio)ureas and squaramides via the dienolate intermediates. This unprecedented 1,3- A nd 1,5-reactivity of dienolates of the ?-aryl-α,β-unsaturated aldehydes led to the formation of cyclohexenol derivatives with four contiguous stereogenic centers and a chiral substituent at C2 with good diastereoselectivities and high ee values. Such reactivities of the dienolates are totally different from those of the corresponding dienamine intermediates.
- Majee, Debashis,Jakkampudi, Satish,Arman, Hadi D.,Zhao, John C.-G.
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supporting information
p. 9166 - 9170
(2019/11/14)
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- Study on anti-proliferative activity in cancer cells and preliminary structure–activity relationship of pseudo-peptide chiral thioureas
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In our previous studies, we have shown that thiourea compounds containing phosphate esters have potent antitumor activity and can be used as a novel strategy for the development of antitumor agents. Herein, a series of novel phosphonate thioureas 5–38 have been synthesized, which were fully characterized by 1H NMR,13C NMR spectrum, elemental analysis. Three human cancer cell lines (Bcap-37, BGC-823, and PC-3) have been used to investigate these compounds’ antitumor activities. After the summarization of the structure–activity relationships, we found that the variation of R, R1, and R2 in these novel phosphonate thioureas contribute to the antitumor activities. All these SAR-guided efforts may lead to novel antitumor drugs in the market in the near future.
- Liao, Peng,Hu, Shi-Qin,Zhang, Hong,Xu, Liang-Bi,Liu, Jing-Zi,He, Bin,Liao, Shang-Gao,Li, Yong-Jun
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p. 300 - 304
(2018/02/15)
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- l-tert-Leucine-Derived AmidPhos-Silver(I) Chiral Complexes for the Asymmetric [3+2] Cycloaddition of Azomethine Ylides
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The l-tert-leucine-derived AmidPhos/silver(I) catalytic system has been developed for the asymmetric [3+2] cycloaddition of azomethine ylides with electronic-deficient alkenes with or without Et3N. Under optimal conditions, highly functionalized endo-4-pyrrolidines were obtained with modest to high yields (up to 99% yield) and enantioselectivities (up to 98% ee).
- Zhou, Zhipeng,Zheng, Xiaojun,Liu, Jialin,Li, Jinlei,Wen, Pushan,Wang, Haifei
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p. 999 - 1003
(2017/05/05)
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- Mechanistic implications of the enantioselective addition of alkylzinc reagents to aldehydes catalyzed by nickel complexes with α-amino amide ligands
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The enantioselective alkylation of aldehydes catalysed by nickel(ii)-complexes derived from α-amino amides was studied by means of density functional theory (DFT) and ONIOM (B3LYP:UFF) calculations. A mechanism was proposed in order to investigate the origin of enantioselectivity. The chirality-determining step for the alkylation was the formation of the intermediate complexes with the involvement of a 5/4/4-fused tricyclic transition state. The predominant products predicted theoretically were of (S)-configuration, in good agreement with experimental observations. The scope of the reaction was examined and high yields and enantioselectivities were observed for the enantioselective addition of Et2Zn and Me2Zn to aromatic and aliphatic aldehydes.
- Escorihuela, Jorge,Burguete, M. Isabel,Ujaque, Gregori,Lledós, Agustí,Luis, Santiago V.
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p. 11125 - 11136
(2016/12/07)
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- Primary amino acid derivatives: Compounds with anticonvulsant and neuropathic pain protection activities
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Pharmacological management remains the primary method to treat epilepsy and neuropathic pain. We have advanced a novel class of anticonvulsants termed functionalized amino acids (FAAs). In this study, we examine FAA derivatives from which the terminal acetyl moiety was removed and termed these compounds primary amino acid derivatives (PAADs). Twenty-seven PAADs were prepared; the central C(2) R-substituent was varied, including C(2) stereochemistry, and the compounds were tested in rodent models of seizures and neuropathic pain. C(2)-Hydrocarbon N-benzylamide PAADs were potent anticonvulsants and excellent anticonvulsant activity (mice, ip; rat, po) was observed for C(2) R-substituted PAADs in which the R group was ethyl, isopropyl, or tert-butyl, and the C(2) stereochemistry conformed to the d-amino acid configuration ((R)-stereoisomer). These values surpassed the activities of several clinical antiepileptic drugs. The C(2) (R)-ethyl and C(2) (R)-isopropyl PAADs also displayed excellent activities in the mouse (ip) formalin neuropathic pain model. Significantly, unlike the FAA structure-activity relationship, PAAD anticonvulsant activity increased upon substitution of a methylene unit for a heteroatom in the R-substituent that was one atom removed from the C(2) site, suggesting that these PAADs function by a different pathway than FAAs.
- King, Amber M.,Salomé, Christophe,Dinsmore, Jason,Salomé-Grosjean, Elise,De Ryck, Marc,Kaminski, Rafal,Valade, Anne,Kohn, Harold
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p. 4815 - 4830
(2011/10/01)
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- Stereoselective nucleophilic addition to imines catalyzed by chiral bifunctional thiourea organocatalysts
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A new and easy synthesis of chiral bifunctional organic catalysts obtained by the combination of (S)-t-leucine-derivatives with (1R,2R)-trans-1,2-diamino-cyclohexane was developed. A few compounds, representatives of a class of organocatalysts containing a thiourea group and a tertiary amino group connected through a chiral backbone, have been successfully synthesized. The catalytic behaviour of such bifunctional chiral molecules, either neutral or protonated species, was investigated in the addition of acetylacetone to β-nitrostyrene as a model reaction. Using the best conditions, high yields and enantioselectivities of up to 85% were obtained. The same metal free catalysts were then employed in the addition of activated nucleophiles to imines: in the reaction of 1,3-diketones with N-CBz imines, the products were isolated in up to 61% ee, while in the reaction with diethyl malonate enantioselectivities up to 71% were reached.
- Puglisi, Alessandra,Benaglia, Maurizio,Annunziata, Rita,Rossi, Davide
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experimental part
p. 2258 - 2264
(2009/04/04)
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- Structure-based analysis and optimization of a highly enantioselective catalyst for the strecker reaction
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A mechanistic investigation of the asymmetric Strecker reaction catalyzed by a metal-free Schiff base catalyst was conducted. The active site of the catalyst, the relevant stereoisomer of the imine substrate, and the solution structure of the imine-catalyst complex were elucidated using a series of kinetics, structure-activity, and NMR experiments. An unusual bridging interaction between the imine and the urea hydrogens of the catalyst was identified and supported by computation. Rational optimization of catalyst structure based on the mechanistic insight led to an improved catalyst for the asymmetric Strecker reaction. Copyright
- Vachal, Petr,Jacobsen, Eric N.
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p. 10012 - 10014
(2007/10/03)
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- Asymmetric catalytic Mannich reactions catalyzed by urea derivatives: Enantioselective synthesis of β-aryl-β-amino acids
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Highly enantioselective addition reactions between silyl ketene acetals and N-Boc aldimines are catalyzed by the thiourea-based catalyst 1c. Extraordinary scope is observed in this methodology with regard to the imine substrate, with aryl and heteroaromatic derivatives generally affording nearly quantitative yields of β-amino ester product in up to 98% enantioselectivity. Copyright
- Wenzel, Anna G.,Jacobsen, Eric N.
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p. 12964 - 12965
(2007/10/03)
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